Flowmeters, and particularly rotameters, measure the volume of flowing fluids. These flowmeters are usually used in the medical field when it is important to be able to measure or check that a given volume of fluid is flowing uniformly and in a determined manner. Obviously, this type of instrument can also be used in other domains, such as analysis laboratories, research laboratories, etc.
This type of device usually comprises a body, a flow detector and a flow adjuster. Following the direction of fluid circulation, the body includes fluid circuits between a body inlet, the flow detector, the adjuster and a body outlet. The flow detector usually includes a graduated tube inside of which there is a ball with an appropriate size and weight. The fluid enters through the bottom of the tube and exits through the top. The fluid that enters this type of device is at a low pressure between approximately 0 and 10 bars.
Flowmeters usually include fluid flow adjustment devices, if possible enabling very fine and even very low flow adjustments. These devices associated with flowmeters usually include a valve device with a needle valve, with a metal-to-metal needle or a conical needle closing off a fluid passage orifice. Thus, the fluid passage is partly obstructed by the valve or the needle for which the engagement depth in the passage orifice defines the fluid passage cross section.
However, since this type of device with a conical closing needle is very fine, it is also fragile and is difficult to make in production series. Furthermore, these valve or needle devices tend to develop play in the long term, degrading the adjustment precision and the long-term stability.
Another disadvantage of these devices is the presence of a leak tightness bell included therein on the measurement tube. This bell is an element separate from the rest of the device and requires seals that can cause leak tightness problems.
Fluid distribution flow adjustment installations are also known in which the fluid inlet tube opens onto a disk perforated with a row of holes with increasing diameters that can be placed in turn facing the fluid inlet tube by using a knurled knob that discretely and discontinuously increases the fluid flow. This embodiment does not enable a continuous and gradual increase, since it includes a risk of interrupting the flow when none of the holes in the disk is in front of the fluid inlet tube. This is a major disadvantage when the fluid flow being distributed is vital for a living being.